Secure and usable mutual authentication systems have been demanded in order to perform ad hoc data transmission between devices having a wireless interface. The following examples have been known as technology relating to such mutual authentication systems.
For example, some techniques using PIN (Personal Identification Number) have been known for mutual authentication between devices having a wireless interface. Those techniques are hereinafter referred to as “Related Art 1.”
As in Patent Literature 1, there have also been known techniques of detecting whether a button provided in a device is pushed, generating a unique group connection ID, and using the unique group connection ID as a common key (authentication key) for mutual authentication. Those techniques are hereinafter referred to as “Related Art 2.”
In Non-Patent Literature 1, devices each having a non-contact IC reader are held up over each other to exchange keys. The devices mutually use those keys as authentication keys. Those techniques are hereinafter referred to as “Related Art 3.”
Patent Literature 2 and Non-Patent Literatures 2 to 6 disclose means using an acceleration sensor, which is more advantageous in implementation cost than a non-contact IC reader. In those references, the same motion is supplied to two devices having an acceleration sensor from an external source (for example, those devices are vigorously shaken). Thus, a common variation is shared with those devices. Based upon such a common variation, an authentication key is shared with those devices. Those techniques are hereinafter referred to as “Related Art 4.”
In Related Art 1, data with a large number of digits should be inputted without any error in order to obtain high cipher strength by a sufficient key length. Such a process is troublesome and difficult. Therefore, there has been a problem in usability.
In Related Art 2, to push a button is a process that can readily be performed by anyone. When a button is accidentally or intentionally pushed by a third party, an authentication key is needlessly provided to the third party. Thus, there has been a problem in security.
In Related Art 3, a non-contact IC reader should be mounted on each of devices that are to be subjected to mutual authentication. Thus, there has been a problem in cost for those devices.
In Related Art 4, a user should aggregately hold two devices and vigorously shake those devices. Such an operation may be difficult in itself.
Furthermore, in Related Art 4, since two devices are aggregately held, many restrictions are imposed on the size, shape, weight of the devices, and the like. In order to apply this technology to a device, the device should have a size and a shape that allow two devices to be held aggregately. Thus, it is difficult or even impossible to apply this technology if one of two devices is a fixed device or if any one of two devices has a shape, size, or weight that makes it difficult to hold those two devices aggregately.
Moreover, in Related Art 4, since two devices are aggregately held and shaken, each of the devices should have a resistance to such vibration. Generally, a user of a device is not specified in a design phase. Supposing that an unspecified user vibrates a device, the device should be designed with some margins of the vibration resistance in consideration of individual differences in amplitude or speed of vibration to be applied. In this regard, there is also a restriction on design of the device.